Bruel & kjaer 1022 User guide

\

B~at

Frequency Oscillator Type 1022

A

beat

frequency

oscillator covering

the

range

20

to

20ooo

c/s. The

apparatus

is

designed

to

meet

the

numerous

requirements

of

a signal

source

for

audio

frequency

work.

It

is

excellently

suited

both

for

electrical

and

electroacoustical

measurements

, as well

as

for

acoustic research.

BRUEL

&

KJJEK

Ncerum, Denmark .

eye

80

05

00

.

~

BRUKJA,

<;:openhagen . Telex: 5316

BB

1022

Beat Frequency

Oscillator

Type 1022

JUNE

1963

Contents

Page

Description

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

General

5

Description

of

the

Oscillator

and

Mixer-Section

. . . . . . . . . . . . . . . . . . . . 6

Partial

Blocking

of

Frequency

Range

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Description

of

the

Output

Amplifier

Section

......................

10

Power

Supply

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

()peration

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13

General

........................................................

13

Calibration

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14

Operation

Using

the

Output

Terminals

Marked

LOAD

............

14

Operation

Using

the

Built-in

Attenuator

.........

.

.............

..

. 15

Frequency

Modulation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15

Automatic

Recording

............

..

..............................

16

Automatic

Regulation

of

the

Output

Power

........................

19

Remote

Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Trouble

Shooting

..........................................

."

.....

21

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21

Output

Transformer

TU

0005

..

.

...

.

...

.....

.

.. ..

................

21

Applications

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Group

A.

Electronic

Measurements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Measurement

of

Frequency

Response

of

Four-Terminal

Networks

..

22

A.C.

Bridge

Measurements

........................................

23

Measurement

of

Gain

in

A.F.

Amplifiers

...........................

25

Group

B.

Acoustical

Measurements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Recording

of

the

Frequency

Response

of

Loudspeakers

. . . . . . . . . . . . 26

Recording

of

the

Frequency

Response

of

Microphones

. . . . . . . . . . . . 27

Recording

the

Frequency

Characteristic

of

Hearing

Aids

and

Ear-

phones

..

.

..................................................

28

Checking

of

Hearing

Aids

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Measurements

on

Air

Filters,

Carbureltor

Inlets

etc

.................

31

Testing

the

Qualities

of

Airborne

Sound

Insulation

................

33

Measurement

of

Reverberation

Time

..............................

33

Frequency

Calibrated

Paper

......................................

35

Non-Frequency

Calibrated

Paper

................................

37

Use

of

the

Protractor

SC 2361

....................................

37

Absorption

Measurement

of

Sound

Insulation

Material

............

38

Group

C.

Mechanical

Measurements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Strain

Measurement

on

Vibrated

Objects

. .

...

.....

..

......

...

. . 40

Instrument

Combinations

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Descripti~n

............................

.

..........

....

..

...

....

42

The

Audio

Frequency

Spectrometer

..............................

43

The

Microphone

Amplifier

...........................

.......

...

..

H

The

Level

Recorder

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-1-5

Recording

Paper

.......

....

................................

.

....

46

Ope,

ration

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

General

........................

.

...............................

47

Synchronization

.....

..

..........................................

47

Applications

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

49

Automatically

Recording

Harmonics

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Vibration

Measurements

...................

..

.....

...........

52

Noise

Measurements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Specification

.......................

. . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Description

General.

The

Beat

Frequency

Oscillator

Type

1022 is

primarily

designed

for

electrical

and

electro-acoustical

measurements.

It

works

on

the

heterodyne

principle

using

two

bigh

frequency

oscillators,

o

'ch

o

erates

on

a

fixed

frequenc

while

the

f

uency

of

the

other

can

be

altered

b a

variable

ca

acitor,

The

required

audio

frequency

IS

en

obtained

as

the

difference

between

the

hvo

~igh

frequencies

and

can

~~_!_~:ld

off

a

large

illuminated

~c

-

~

th~p~i

nter

~f

-

whichTs

-

c

-

~

-

~~~de(Ct~

-

th

-

;

-

vari

_

~Qle

~

capa:!~Jjie

:O

S.ci~1s

lo~arit~

~g~aduated

from

20

to

20oo;;

-·

c/

s.

An

INCREMENTAL

SCALE

is

also

provided,

allowing

exact

frequency

selection

~

in

the

range

-50

to

+50

c/s

around

any

setting

on

the

main

scale.

The

zero-adjustment

is

controlled

by

-

~~~

inin

[3_~

-

~.ll

_

Ll)

_

Ert_w_e_en_j

h.e.-f.l:eq-t!.m

G-y

'

of

the

__

!fiains

voltage,

and

that

of

-

th~

--

<>.~<:?i!!~!9

_

~

volta~e

.

occuring

w~

~

-

~

__

the

--

~~ii

-

la!Qr._i;_i;med

.to

±hi

lr~q~

-

~~~y

-

~f

the

mains

;~d

--

th~

--:

p

-

ress

~

~tton

-

~arked

PoWER

FREQUEN

cv BEA-T

~~

~_i!l

_

t:

__

frunLl>_a

neL;;

Ti~~ii~"}

~

-

presse~.

The

variable

capacitor

has

two

control

knobs,

one

of

which

is

in

a

fixed

position

on

the

capacitor

spindle

and

is

used

for

quick

setting

to

the

de-

sired

freguency

..

The

other

will

,

when

depressed,

rotate

the

spindle

\vith

a

_r.a_tio

of

1,

to

5

giving

greater

accuracy

and

fine

selection

of

the

frequency.

A

worm

gear

permits

the

~:l__Eac

itor

to

be

tuned

automa~

.

!~

-

~

!!L

_

Jor

example,

with

the

aid

of

the

motor

of

the

Level

Recorder

Type

2305.

The

mechanical

connect:rorl

-

To

-

Tl1e

--

Levcl

___

Re-

corder

-is

effected

by

means

of

a

fl

~~~

haft

.

'-------------·-··-

···-·-

·-··· -

------

..

·-··· .. ···- . •

..

' . . .

.,

which

can

be

screwed

onto

the

bushing

on

the

side

of

the

Oscillator's

cabinet.

The

-

worm

g;;~~

-

~~-;_:;

-

b

-

e

--

enga:gea

-·

a

nd

rele

{\

-

sed

--

w1ill11i

e -

aTCi

___

o

f'

_a.buil't

-=-

i;

electromagnetic

clutch,

operated

from

a

switch

on

the

front

panel

marked

AUTOMATIC

SCANNING,

or

by

a

remote

control

arrangement.

The

electro-

-

magnetic

clutch

is a

friction-device

allowing

manual

tuning

of

the

variable

capacitor

even

when

the

clutch

is

engaged.

Being

also

designed

for

use

in

room-acoustical

measurements,

the

Beat

Fre-

quency

Oscillator

is

equipped

with

frequency

modulation,

for

which

a

re-

actance

tube

controlled

by

saw

-

tooth

oscillations

from

a

built-in

oscillator

is

switched

into

the

circuit

of

the

fixed

oscillator.

Both

the

frequency

and

the

amp-litude

of

the

saw-tooth

oscillation

are

adjustable

and

may

be

read

off

two

printed

dials.

Provision

is

also

made

for

external

modulation,

whereby

very

wide

limits

of

frequency

modulation

can

be

obtained.

By

means

of

a comp.!_essor

circuit,

which

~

can

be

controlled

from

an

~

~~t~ge,

it

is

possible

t~voltage,

current,

or

sound

pre

-

ssure

constant

during

measurements

when

using

the

oscillator

as

a

power

source.

5

Description

of

the

Oscillator·

and

Mixer-Section.

Fig. 1.1

shows

a

block

diagram

of

the

complete

Oscillator

.

The

fixed

oscillator

is

tufied

to

120 k

c/s

and

can

be

frequency

modulaled

.

The

reactance

tube

circuit

acts

as

a

variable

inductance

and

the

modulation

swing

can

be

varied

from

0

to

± 250

c

/

~y

means

of

a

switch

on

the

front

panel

of

the

apparatus,

marked

FREQUENCY

DEVIATION.

By

means

of

the

switch

marked

MODULATION

FREQUENCY

the

frequency

of

the

built

-

in

saw-tooth

oscillator

may

be

chosen.

Frequencies

of

1-

1.6--2.5

-4-6.

3-

10-16

and

25 c/s

are

available.

The

oscillator

is a

blocking

type,

tuned

to

approximately

7 Mc/s,

and

Lhe

frequency

of

the

saw-tooth

oscilla-

tions

is

set

by

changing

the

grid

resistor.

Fixed Variable

)J

Oscillator

Amplifier

Regulating

Amplifier

Mixer

Low Pass

Filter

Variable

Oscillator

I

Impedance

Output

Matching

Amplifier

Circuit

Ref.Sig. Remote

1000c

;

~l

~

Fontrol

I

Magnetic

:

Clutch

1

I

Output

Attenuator

Load

Output

Attenuator

Output

Fig. 1.1.

Block

Diagram

of

the

Beat

Frequency

Oscillator 1022.

Provision

is

made

for

external

modulation.

The

external

generator

should

then

be

connected

to

two

terminals

of

the

socket

on

the

front

plate

marked

REMOTE

CONTROL.

For

external

modulation

a

voltage

of

approximately

3.5

volts

is

necessary

when

a

modulation

swing

of

± 250

c/s

is

required.

When

external

modulation

is

etmployed

the

switch

marked

MODULATION

FREQUENCY

must

be

in

position

"Ext.

Mod.",

as

in

this

position

of

the

sw

itch

the

reactance

tube

is

on

and

the

saw-tooth

oscillator

is

off.

A

variable

capacitor

inserted

in

the

tuned

circuit

of

the

fixed

oscillator,

arid

operated

by

the

knob

marked

FREQUENCY

INCREMENT,

permits

exact

frequency

selection

in

the

range

.± 50 cis

for

any

setting

on

the

main

scale.

Thus,

using

this

capacitor,

frequencies

down

to

zero

may

be

obtained

,

even

t!J.ough

the

main

scale

is

only

calibrated

from

20

c/s

to

20ooo

cis:

By

means

of

a

noiseless

switch

on

the

front

panel,

marked

OSCILLATOR

STOP,

the

voltage

on

the

anode

of

the

120

kc

/s

oscillator

can

be

disconnected.

6

This

switch

is

specially

provided

for

reverberation

measurements

.

The

same

method

is

used

for

remote

control,

the

appropriate

wiring

of

which

can

be

seen

by

referring

to

the

circuit

diagram

of

the

Oscillator.

MAX.

METER

DEFLECTION

OUTPUT

LEVEL

dB

10

/Distorted

----------,~

Signal

0+----------------'r--------------

-10 +---------

-20

-30+--------

-40

-50+--------

-60

-70

-so

-90

---r--~-r--~-r--~-r~~-r~r-~~-v

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Q.9

Comp.

Voltage

on

.

..

Compressor" Input"

(63632

(

..

Compressor Voltage"

on

maximum)

Fig. 1.2.

Regulation

characteristics for

different

positions

of

the

potentiometer

marked

OUTPUT

LEVEL.

7

The

output

voltage

from

the

fixed

oscillator

is

fed

to

the

grid

circuit

of

a

pentode,

the

grid

bias

of

which,

is

controlled,

by

means

o'f a

regulating

amplifier

.

To

obtain

a

higher

degree

of

control

the

working-point

of

the

pentode

is

chosen

on

the

non-linear

portion

of

the

Ia-Eg

characteds

1tic,

near

cut-off.

The

purpose

of

this

circuit

is

to

control

automatically

the

output

power

of

the

Beat-Frequency

Oscillator

by

an

A.F

.

control

voltage.

For

example,

th

e

voltage

from

a

standard

microphone

placed

in

the

sound

field

of

a

loud-

speaker

which

is

fed

from

the

Oscillator.

In

this

case

the

output

power

of

the

Oscillator

will

be

so

controlled

that

a

cons

tant

sound

pressure

is

main-

tained

on

the

standard

microphone.

The

A.F.

control

voltage

should

be

fed

onto

the

screened

socket

marked

COMPRESSOR

INPUT

on

the

front

panel

of

the

Oscillator.

A

variable

potentiometer,

marked

COMPRESSOR

VOLTAGE

is

inserted

in

the

input

circuit

of

the

regulating

amplifier

and

can

be

used

as

volume

control

for

the

output

power

fron1

the

Oscillator

when

automatic

regulation

is

employed.

Care

must

be

taken

,

not

to

use

a

modulated

DC

voltage

as

regulation

voltage

,

as

the

input

circuit

is

directly

coupled.

The

regulating

amplifier

has

a

linear

frequency

characteristic

from

20 to

20ooo

c/s

and

should

have

an

input

signal

of

approximately

o.5

volt

on

the

grid

of

.

the

A.F.

amplifier

tube

for

full

regulation.

The

input

impedance

,

measured

across

the

terminals

of

the

socket

marked

COMPRESSOR

INPUT

i,s

approximately

25 k.Q,

and

the

maximum

obtainable

range

of

regulation

is 50 dB.

The

amplified

A.F.

control

voltage

is

rectified

in

a

full-wave

rectifier,

designed

to

give a DC

output

voltage

prop

,

ortional

to

the

average

value

of

the

A.F

.-co

ntrol

voltage.

By

means

of

the

switch

marked

COMPRESSOR

SPEED

on

the

front

panel

of

the

oscillator

the

regulation

speed

can

be

varied.

Regulation

speeds

of

30-

100-300

or

lo

co

dB/s

may

be

chosen

by

ehanging

the

Yalue

of

the

resistor

in

the

A-C

filtering

network

for

the

rectified

control

voltage.

When

the

switch

COMPRESSOR

SPEED

is

in

position

"comp.

off."

the

output

from

the

rectifier

is

short-circuited

thereby

disconnecting

the

automatic

regulation

circuit.

To

make

linear

regulation

of

the

output

level

possible,

even

when

maximum

output

power

is

required

from

the

Oscillator

,

the

level

of

the

high

frequency

voltage

from

the

120

kc

/s

fixed

Oscillator

is

raised

approx.

10

dB

when

the

automatic

compression

is

switched

in.

The

anode-circuit

of

the

pentode

in

the

variable-,u

amplifier

is

tuned

to

120

kc

/s,

forming

a

band-pass

filter,

the

output

of

which

is

fed

to

the

mixer.

In

the

mixer

tube,

which

is

one

half

of

a

twin

triode,

the

120

kc/s

voltage

is

mixed

with

the

output

voltage

from

the

variable

oscillator

.

The

frequency

0f

the

variable

oscillator

can

be

altered

continuously

from

120

to

100·

kc/s

by

means

of

a

specially

designed

variable

capacitor.

This

capacitor

is

made

with

a

high

degree

of

accuracy

and

a

maxi

r

mum

deviation

of

o.7

degrees

8

from

a

logarithmic

frequency

curve

is

obtained.

A

worm

gear,

connected

to

the

capacitor

spindle,

permits

automatic

tuning

with

the

aid

of

an

external

motor,

for

example

the

motor

in

the

Level

Rec

order

Type

2305,

and

the

worm

gear

can

be

set

and

released

by

means

of

a

magneHc

clutch.

This

is

operated

from

a

switch

on

the

front

panel

of

the

oscillator

,

or

it

can

be

operated

from

an

external

switch

or

relay.

Connection

must

then

be

made

to

the

appropriate

terminals

of

the

socket

marked

REMOTE

CONTROL

on

the

front

panel,

and

the

control

switch

AUT.

SCANNING

for

the

magnetic

clutch

must

be

in

position

"

off"

.

The

end

of

the

scale

pointer

spindle

is

provided

with

a 6 nHn'

hole

.

The

arrangement

can

be

used

for

special

purpose

devices

which

are

to

be

governed

by

the

angular

position

of

the

frequency

scale

pointer.

By

means

of

a

pushbutton

marked

1ooo

c/s

REF.

SIGNAL,

an

extra

capacitor

is

introduced

in

the

tuning

circuit

of

the

variable

oscillator.

There

will

be

exactly

1ooo

c/s

at

the

output

socket

when

the

scale

pointer

is

set

to

1ooo

c/s

REF

.

SIGNAL

and

the

pushbutton

looo

c/s

REF.

SIGNAL

is

depressed

.

The

reason

for

setting

the

scale

pointer

at

looo

c/s

REF

. SIGNAL is

in

order

to

be

able

to

align

the

1022

with

the

frequency

calibrated

paper

,

used

on

the

Level

Recorder

Type

2305,

as

this

paper

is

calibrated

from

10 c/s.

The

di

·

stance

between

the

calibration

mark

of

10 c/s

and

20 c/s

on

the

recording

paper

corresponds

to

the

distance

between

looo

c/s

REF.

SIGNAL

and

20 c/s

on

the

oscillator.

By

depressing

the

pushbutton

it

is

now

possible

to

check

that

the

level

of

the

middle

frequencies

is

within

the

divisions

of

the

paper.

The

voltage

developed

across

the

grid

of

the

variable

oscillator

is

fed

into

the

mixer

tube

and

mixed

with

the

voltage

from

the

variable-

.,u

amplifier

.

The

mixer

tube

is

of

fhe

triode

type,

whereby

a

low

hum

level

is

obtained

in

spite

of

the

AC-he

•

ating

of

the

filament.

A

low-pass

filter

having

a

cut-off

frequency

of

50

kc

/s

is

inserted

in

the

anode

circuit

of

the

mixer

tube,

thus

passing

only

the

lower

frequenc

y

obtained

by

the

frequency

conversion,

onto

the

grid

of

the

first

tube

in

the

output

amplifier

section.

Partial

Blocking

of

Frequency

Range.

As

previously

mentioned,

the

frequency

scale

is

logarithmic

and

calibrated

20-20~)00

c/

s.

When

the

capacitor

is

set

to

frequencies

above

20ooo

c/s

or

below

20

c/s

the

fixed

Oscillator

can

be

blocked,

and

consequently

no

output

voltage

will

be

obtained.

For

automatic

recording

of

frequency

characterisrtics,

i.e.

when

using

the

Level

Recorder

Type

2305,

this

is a

great

advantage

as

no

unwanted

curves

will

then

appear

on

the

corresponding

section

of

the

frequency

calibrated

paper.

The

cut-off

section

can

be

made

wider

by

adjusting

the

cam

discs,

connected

to

the

rear

end

of

the

capaoitor

spindle.

However,

if

the

REMOTE

CONTROL

plug

is

removed

there

will

be

no

blocking

at

any

part

of

the

scale.

In

application

where

the

'

B.F.O.

is

employed

in

conjunction

with

the

B & K

Level

Recorder,

and

where

automatic

recording

is

required,

the

blocking

arrangement

can

also

be

used

for

remote

lifting

of

the

Level

Recorder's

writing

pen.

This

is

a

great

asset

in

for

exa

1

rnple

measurements

where

the

compres

,

sor

circuit

of

the

B.F.O.

is

used.

In

this

instance

the

pen-lifting

arrangement

of

the

Le

~

vel

Recorder

can

be

controlled

from

the

frequency

blocking

circuit

by

making

the

appropriate

connections

to

the

REMOTE

CONTROL

jack

of

the

B.F.O.

In

cases

where

the

entire

frequency

range

(20-20ooo

c/s)

of

the

B.F.O.

i's

utilized,

the

normal

frequency

blocking,

which

functions

outside

the

scale

graduation,

should

be

set

out

of

operation.

The

writing

pen

of

the

Level

Recorder

can

now

be

lifted

from

the

paper

outside

the

frequency

range

of

intere

~

st

and

a

proper

working

of

the

com-

pressor

also

at

the

initial

frequency

(20 c/

s)

i

~

s

ensured

during

the

a~tomaHc

scan.

If

the

described

method

is

not

utilized

,

the

following

would

take

place:

No

signal

will

be

present

in

the

range

20ooo

c/s

to

20 c/s

(outside

the

scale

graduation),

i.e.

the

compressor

of

the

B.F.O.

will

be

in

such

a

condition

to

give

full

output

signal

of

the

B.F.O.

Consequently,

when

the

scale

pointer

goes

ins

,

ide

the

scale

graduation

(20 c/

s)

full

output

level

will

be

transmHted

at

20

c/s,

and

after

the

chosen

time

delay

(Compressor

Speed)

the

signal

level

will

be

compressed

to

the

proper

(preset)

value.

A

deflection

on

the

recording

paper

which

is

not

a

response

of

the

measured

object

would

thus

be

recorded.

Description

of

the

Output

Amplifier

Section.

The

voltage

from

the

low-pass

filter

is

fed

to

the

control

grid

of

the

f~rst

tube

in

the

two-stage

audio

frequency

output

amplifier

via

a

variable

potentiometer.

This

potentiometer

is

operated

by

the

knob

marked

OUTPUT

LEVEL

on

the

front

panel

of

the

Oscillator

and

is

used

for

continuous

adjustment

of

the

output

power.

The

gain

of

the

amplifier

is

stabilized

by

means

of

negative

voltage

feedback,

and

the

anode

circuit

of

the

output

tube

is

coupled

to

an

auto-transformer

for

impedance

matching.

Four

different

output

impedances

are

available

and

can

be

chosen

with

the

switch

on

the

front

panel

marked

MATCHING

IMPEDANCE.

The

different

positions

of

the

switch

are

indicated

by

6,

60, 600

and

6ooo

ohms

respective-

ly,

and

the

output

voltage

is

taken

from

the

,

terminals

marked

LOAD.

It

should

be

noted

that

the

output

impedance

of

the

Oscillator

i,s

only

approx-

imately

10-20%

of

the

indicated

value

's,

but

when

loading

with

impedances

as

marked,

a

maximum

output

power

is

obtained

with

a

minimum

harmonic

oontent.

Furtherm10re,

correct

loading

ensures

the

output

voltage

to

be

practically

independent

of

the

frequency.

10

0/o

0.5

5 0.2

0

~

0.1

0

Gl

10.05

z

---

=

Typical

Distortion

Curves

------

•

Guaranteed

Upper Limit

I

~02

®1+-------------~------------~----------~~-------

10

100

--Frequency

1000 10000 f

C/s

16107,2

Fi

g.

1.3.

Distortion

c

uw

es for d

iff

e

rent

loads.

Tlw

curve

marked

"Att.

10 volts"

is

obtained

from

·

measurem

e

nts

taken

on

the

ATTENUATOR

OUTPUT

terminals

open

circuit.

A

fifth

position

of

the

switch

MATCHING

IMPEDANCE

is

marked

"Alt."

and

connects

the

output

transformer

to

an

attenuator,

variable

in

steps

of

10

dB

from

120

,

ftvolts

to

12

volts,

and

is

operated

by

the

switch

marked

ATTEND-

A

TOR

on

the

front

panel.

With

the

impedance

sw

itch

in

this

position

the

output

circuit

is

connected

to

the

sc

re

e

ned

socke

t

on

top

of

the

front

panel,

the

output

impedance

being

constan

t

and

approximately

50

ohms.

The

overall

accuracy

of

the

attenuator

is

approxima

t

ely

2

%.

The

voltage

on

the

output

terminals

is

indicated

by

a

vacuum-tube

voltmeter

which

measures

the

average

value

of

the

A.F.

voltage.

It

is

calibrated

in

r.m.s.

va

lue

s

of

a

sinusoidal

voltage,

and

the

accuracy

in

the

frequency

range

20'-20ooo

c/s

is

1.5 %

of

full

scale

deflection.

In

addition

to

the

voltscales

there

is

also

a

dB

scale,

and

the

scale

is

ca

librat

ed

in

such

a

way,

that

it

is

possible

to

read

directly

the

level

in

dB

re.

1

volt.

The

sensitivity

of

the

voltmeter

is

automatically

changed

when

the

position

of

the

switch

marked

MATCHING

IMPEDANCE

is

altered.

Full

defle

c

tion

of

the

meter

is

indicated

on

the

switch.

When

the

MATCHING

IMPEDANCE

switch

is

in

position

"Att."

the

output

voltage

available

from

the

Oscillator

will

depend

on

the

position

of

the

A

TTENU

A

TOR

switch,

in

this

case

full

deflection

of

the

meter

corresponds

to

the

value

indicated

by

the

sw

itch

position.

11

[n

addition

to

th

e

volt

calibration

on

the

switch

ATTENUATOR

OUTPUT

there

is a1so a

dB

calibration,

and

the

calibration

is,

as

mentioned

above,

given

in

dB

re.

1

volt.

An

example

will

explain

the

use

of

the

dB

scale:

If

the

OUTPUT

LEVEL

is

adjusted

in

such

a

way,

that

20 dB is

read

on

the

meter

scale,

and

the

s

witch

ATTENUATOR

OUTPUT

is

in

the

position

-

30

dB

th

en

the

signal

level

at

the

output

soc

ket

will

be

20

-3

0 = -10

dB

re. 1

volt

(o.316 V).

The

signal-to-noise

ratio

of

the

Oscillator

is

greater

than

70

dB

for

maximum

output

voltage.

It

is

independent

of

the

position

of

the

attenuator,

but

some-

what

dependent

on

the

position

of

the

potentiolffieter

marked

OUTPUT

LEVEL.

The

best

result

is

obtained

when

the

voltmeter

has

a

deflection

around

20 dB.

Harmonic

distortion

is

dependent

on

the

setting

of

the

OUTPUT

LEVEL

potentiometer.

As

long

as

the

output

is

kept

within

the

meter

range,

the

distortion

will

be

of

the

order

indicated

in

Fig.

1.3.

Power

Supply.

The

Oscillator

can

be

operated

from

a 240, 220, 150, 127, 115

or

100

volts

AC

power

line,

the

power

consumption

being

about

60

watt

s.

The

proper

voltage

is

selectable

by

a

switch-fuse

combination

situated

at

the

rear

of

the

instrument.

To

select

the

voltage

it

is

necessary

to

remove

the

fuse

by

turning

the

hexagonal

disc

head

in

the

centre

of

th

e

sw

itch

anti-

clockwise.

Then

turn

the

head

of

the

voltage

adjuster

with

a

co

in

until

the

white

mark

is

aligned

with

the

required

voltage.

The

fus

e is

th

en

replaced.

It

should

be

noted

that

if

the

aparatus

is to

be

operated

from

a DC

power

line,

or

from

an

accumulator,

a

vibrator

unit

or

a

rotary

converter

is

required.

12

•

Operation

General.

Ascertain

that

the

Beat

Frequency

Oscillator

is

set

to

the

appropriate

power

supp

ly

voltage

by

means

of

the

selector

at

th

e

rear

of

the

instrument,

and

af

t

er

connection

to

th

e

power

supply,

the

instrument

can

be

switched

on

by

the

toggle

switch

marked

POWER

on

the

front

panel.

The

dial

lights

in

th

e

meter

,

and

frequency

scale

shou

ld

come

on

immediately.

Power

Automatic

Sconning

Remote

Control

--

-J

H-"L-

-"

~r=====+=~======~======~~

Compressor

Speed

lFrequency

Scale

Alignment

Attenuator

Output

Attenuator

Impedance

Switch

Load

Compressor

Voltage

Compressor

Input

Output

!6

:J

67cJ

Fig. 2.1.

Control

knobs

and

markings

of

the

Beat

Frequency

Oscillator

Type

1022.

13

A.

Calibration.

1.

Snap

the

toggle

switch

marked

POvVER

to "

on"

and

allow

two

minutes

warm

up.

2.

MODULATION

FREQUENCY

and

COMPHESSOR

SPEED

to

their

"off"

position.

3.

Turn

main

scale

pointer

until

it

is

on

the

frequency

of

the

line

voltage

(e.g.

50

or

60

c/s),

checking

that

the

frequency

incremental

scale

is

on

zero.

If

not,

set

by

FREQUENCY

INCREMENT

knob

to

this

point.

4.

Set

suitable

deflection

on

the

:n1:eter

by

tuning

the

knob

marked

OUTPUT

LEVEL

to

higher

than

center

scale

reading.

5.

Press

POWEH

FHEQUENCY

BEAT

butlon

and

hold

to

"in"

po

,

sition

and

at

the

same

time

rotate

FHEQUENCY

SCALE

ADJUSTMENT

FINE

slowly,

until

a

large

fluctuation

registers

,

slows

up,

and

practically

ceases

on

the

meter

dial.

If

the

scale

is

widely

out

of

tune,

two

points

may

be

found

where

this

occurs,

only

one

of

which

is

correct

and

therefore

a

check

as

outlined

in

the

following

paragraph

should

be

carried

out,

firstly

releasing

the

POWEH

FREQUENCY

BEAT

button.

6.

Turn

the

main

scale

pointer

to

twice

the

mains

frequency

(100

or

120

c/s)

and

if

improperly

tuned

the

me:er

needle

will

drop

to

zero

indica

-

tion.

Then

FHEQUENCY

SCALE

ADJUSTMENT

FINE

must

be

re-aligned,

but

however,

if

the

other

zero

point

cannot

be

found

and

is

outside

the

range

of

the

FINE

control,

align

the

variable

capacitor

marked

COARSE

with

a

screwdriver

to

give

a

suitable

selling,

which

should

occur

al

some

point

between

4

and

6

on

FREQUENCY

SCALE

ADJUST-

MENT

FINE.

8.

Operation

Us

,

ing

the

Output

Terminals

Mark<'d

LOAD.

Apply

the

following

proceclure:

-

1.

Set-up

and

calibrate

the

oscillator

as

described

in

A.

2.

Place

the

MATCHING

IMPEDANCE

switch

in

a

suitable

position

for

the

application.

N.B.

Full

deflection

of

the

instrument

meter

corresponds

to

the

voltage

indicated

by

the

switch

position.

3.

Connect

the

load

to

the

output

terminals

marked

LOAD.

N.B.

Hight

terminal

is

grounded.

4.

Turn

the

pointer

on

the

main

frequency

dial

to

the

desired

frequency,

finely

adjusting

the

Frequency

Increment

if

necessary.

(For

automatic

frequency

sweep,

see

under

E).

5.

Select

a

suitable

output

voltage

hy

turning

the

knob

marked

OUTPUT

LEVEL.

14:

•

,

C.

Operation

Using

the

Built-in

Attenuator.

Apply

the

following

procedure:

-

1.

Set-up

and

calibrate

the

oscillator

as

described

in

A.

2.

Set

the

MATCHING

IMPEDANCE

switch

in

the

position

"AU.".

3.

Select

the

appropriate

voltage

range

by

means

of

A

TTEN

UA

TOR.

N.B.

Full

deflection

of

the

instrument

meter

corresponds

to

the

voltage

indicated

by

the

switch

position.

4.

Connect

the

load

to

the

screened

output

socket

on

the

top

of

the

instru

-

m.

ent

marked

ATTENUATOR

O

UT

PUT.

5.

Proceed

as

in

B. 4

and

5.

D.

Frequency

Modulation.

When

a

frequency

modulated

output

signal

is

required,

the

following

proce

;

dure

should

be

adopted:-

·

.f

..

0

,.,_..,.

1.

Turn

the

knob

marked

MODULATION

FREQUENCY

to

the

requir

'

ed

frequency

.

2.

Turn

the

knob

marked

FREQUENCY

DEVIATION

to

zero.

3.

Re-calibrate

the

Oscillator

as

described

in

A,

omitting

to

turn

TION

FHEQUENCY

to

"off"

position.

MODULA- ·

0 f

4.

Set

the

FREQUENCY

DEVIATION

knob

to

the

required

bandwidth.

5.

Proceed

as

described

in

B

items

2 to 5,

or

C

items

2 to 5,

dependent

on

the

requirement.

2305

Object

under

test

.

~

':

~

:~-~

:

.

-

:

~

:·

..

~

~-

;:

!

·:

·

:

-

~

!

-

.:

·

~-

!

~

·

:

·

1022

Fig. 2.2.

Example

of

mechanically

connecting

the

B.F.O. 1022 to

Level

Recorder

Type

2305.

15

E. Automatic Recording.

By

combining

B.F.O.

Type

1022

and

Level

Hecorder

Type

2305,

or

using

Automatic

Freq

uen

cy

Response

Recorder

Type

3308,

it

is

possible

to

auto-

matically

record

the

frequency

response

of

four

terminal

networks.

When

using

B.F.O.

Type

1022

and

Level

Recorder

2305,

it

is

necessary

to

connec

t

th

e

two

instruments

mechanically

by

a

Flexible

Shaft

UB 0040

as

in

Fig.

2.2

and

to

make

the

elec

tri

ca

l

connections

also

shown

.

Fig.

2.3

depicts

the

use

of

the

Automatic

Frequency

Response

Recorder

Type

3308

with

th

e

required

externa

l

connections.

For

setting-up,

calibrating

and

synchronising

the

combinaHon

shown

in

Fig. 2.2

the

following

procedure

s

hould

be

adopted:-

1.

Ensure

power

supp

lies

are

correct

and

swi'tch

POWER

toggl

es

to

th

e

"on"

position.

2.

Ca

libr

ate

the

B.F.O.

as

described

in

A.

3308

Object

under

test

Pig. 2.3.

External

electrical

connections

when

using

Automatic

Frequency

Response

Recorder

Type

3308.

3.

Connect

the

instruments

as

shown

in

Fig.

2.2.

This

is

done

by

connecting

a

flexible

driving

cable

(UB 0040) to

the

upper

driving

shaft

of

the

Recorder

DRIVE

SHAFT

I

located

at

:he

right-hand

side

and

to

the

front

of

the

Level

Recorder.

Taking

the

other

end

of

the

cable,

insert

and

screw

into

drive

on

left-hand

side

of

B.F

.O.

(Check

engagement

by

switching

the

Level

Recorder

START

/

STOP

switch

to

"start"

and

the

B.F.O.

magnetic

clutch

to

"

on

"

and

note

if

scale

pointer

rotates

).

Potentlometer

Range

db

Range Potentiometer

Single

Chart-

Cont. Record

Ewnt

Marking

-1'-"--l+-

--

Drive

Shaft Speed

~~~~~~~=1

-------

Remote

Control

-------

1\No-

Channel Selector

Drive

Shaft II

Drive

Shaft I

Fig. 2.4.

Level

Recorder

Type

2305

viewed

from

above.

4.

Switching

PAPER

DRIVE

to

"stop",

continue

with

the

following

proce-

dure

referring

to

Fig.

2.4.

5.

Load

the

Level

Recorder

with

the

desired

recording

paper.

(Follow

instructions

in

Level

Recorder

Manual).

6.

Select

and

insert

required

Range

Potentiometer

. (N.B.

Place

POTENTIO

-

METER

RANGE

dB

switch

to

"standby"

when

changing

potentiameters).

7.

Switch

POTENTIOMETER

RANGE

dB

until

figure

corresponds

to

the

Range

Potentiometer

being

used,

i.e. "

10",

"25",

"50

"

or

"80".

8.

By

means

of

the

switch

RECTIFIER

RESPONSE,

select

R.M.S.

or

if

specially

required

one

of

the

other

three

positions

Average,

Peak,

or

D.C.

9.

Turn

the

LOWER

LIMITING

FREQUENCY

switch

to

the

cut-off

value

(10, 20,

50

or

200

c/s).

10.

Set

WRITING

SPEED

to

required

position.

(Full

explanations

of

items

8, 9

and

10

can

be

obtained

from

the

Level

Recorder

Manual).

17

11.

Place

REVERSE

/

FORWARD

sw

it

ch to

"fo

rward

".

12

.

Select

PAPER

SPEED

to a

suitable

speed,

e.g. 10

mm

/sec.

13

.

Pull

gear-lever

marked

X to

the

outer

position.

(See

Fig.

5.1).

The

actual

paper

drive

speed

now

corresponds

to

the

small

numbers

marked

around

the

PAPER

SPEED

knob.

14.

Two

types

of

recording

can

be

made:

-

(a)

Single

chart

recording

(automatic

recording

over

a

length

of

250

mm

paper

only),

(b)

Continuous

recording

over

any

length

of

paper.

(a)

Single

Chart Recording:

Set

the

PAPER

DRIVE

toggle

switch

to

"start

"

commencing

the

paper

to

run,

which

will

continue

until

the

built-in

automatic

stop

switch

declutches

the

drive

mechanism

(less

than

one

chart

length

).

Reset

recording

paper

by

finger

wheel

Z

(F

ig. 5.1)

until

the

stylus

re

sts

on

the

10 c/s

line.

A

chart

of

250

mm

length

will

now

run

off

when

the

SINGLE

CHART

-

CONTINUOUS

RECORDING

pushbutton

is

pressed

and

released

again

immediately

afterwards.

(It

is

possible

to

stop

the

recording

at

any

Lime

by

setting

the

PAPER

DRIVE

toggle

switch

to

"s

top").

(b)

Continuous

. Recording:

The

operator

should

follow

the

instructions

outlined

under

(a),

i.e.

SINGLE

CHART

RECORDING,

except

that

to

start

the

re-

cording

it

is

necessary

to

press

the

SINGLE

CHART

-CON-

TINUOUS

RECORDING

push-button

and

turn

it

clockwise.

Recording

will

now

automatically

take

place

until

the

push-

button

is

released

again

and

the

PAPER

DRIVE,

START-STOP

toggle

switch

is

set

to

"stop".

Note:

Whenever

the

PAPER

DRIVE

,

START-STOP

toggle

switch

is

in

the

"stop"

position

the

paper

drive

is

completely

con-

trolled

by

the

SINGLE

CHART

-

CONTINUOUS

RECORDING

push

-

button.

15.

In

order

to

synchronise

the

units

,

stop

the

paper

so

that

the

stylus

rests

on

the

10 c/s

line.

16.

Adjust

the

commencing

of

the

reference

line

on

the

paper

to a

suitable

level,

any

necessary

fine

adjustment

being

made

with

the

Input

Potentio-

c;

meter

.

17

.

Set

the

pointer

of

the

B.F.O.

on

1ooo

c/s

REFERENCE

SIGNAL

and

engage

the

magnetic

clutch

by

use

of

the

clutch

switch.

The

units

·

should

then

be

synchronised.

18.

Push

the

1ooo

c/s

REF

.

SIGNAL

button.

The

B.F.O

.

then

generates

a

signal

of

1ooo

c/s

enabling

the

operator

to

select

a

reference

signal

18

.

..

BRUEL & KJAER 1022 User guide

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